Well with no signal, I don't see the high harmonic content. And with an easy load I don't even at 1V out, the tougher load I do but only as I increase the volume to give ~.5V across the 32ohm load on the secondary..

So with the lower load as I increase the grid ac input I am pushing the tube into oscillation or the SSHV into oscillation ?

Hi Salas,
Hope things are ok at your end. I'm in the process of building a 26 pre-amp. My current HT raw supply delivers about 305V at no load and sag down to 210V at 45mA roughly. The supply impedance is about 2K1. My current CLCLC filter smooths the ripple down to 12mV (rms) which is great.

My pre-amps needs 170V and consumes about 7mA per channel. based on your design, I set the shunt current to 40mA. From the simulation it seems that the circuit can regulate fine with the 40V difference. The HT may sag a bit more in practice, so may end up with a 30V difference or so. Will this be OK?

At the moment I used the IRFP9240 but I'm planning to use the FQP3P50 PMOS, but couldn't find the spice model for this....

Sure, I have shown schematic in the past. As in the other regs. SSHV2 will have as standard, if proven it mixes well. But I will have to go visit a friend that has #26 and horn speakers, and tweak there, compare SSHV installed already, gather opinion etc. Want to keep it comparably low parts count with gains in frequency etc. with no further stages, to can practically give better subjective impression also. A juggling act on trying to surely practically improve on a so widely liked and used circuit, not easy.